diff --git a/src/main/resources/assets/opencomputers/loot/openos/boot/00_base.lua b/src/main/resources/assets/opencomputers/loot/openos/boot/00_base.lua
index 7bd7b3aba..0709614b4 100644
--- a/src/main/resources/assets/opencomputers/loot/openos/boot/00_base.lua
+++ b/src/main/resources/assets/opencomputers/loot/openos/boot/00_base.lua
@@ -34,7 +34,7 @@ function print(...)
   local stdout = io.stdout
   local pre = ""
   for i = 1, args.n do
-    stdout:write(pre, tostring(args[i]))
+    stdout:write(pre, (assert(tostring(args[i]), "'tostring' must return a string to 'print'")))
     pre = "\t"
   end
   stdout:write("\n")
diff --git a/src/main/resources/assets/opencomputers/loot/openos/lib/core/full_vt.lua b/src/main/resources/assets/opencomputers/loot/openos/lib/core/full_vt.lua
index ee4b4f494..6e95d685a 100644
--- a/src/main/resources/assets/opencomputers/loot/openos/lib/core/full_vt.lua
+++ b/src/main/resources/assets/opencomputers/loot/openos/lib/core/full_vt.lua
@@ -35,8 +35,16 @@ end
 
 -- [Line;ColumnH  Move cursor to screen location v,h
 -- [Line;Columnf  ^ same
-rules[{"%[", "%d+", ";", "%d+", "[Hf]"}] = function(window, _, y, _, x)
-  set_cursor(window, tonumber(x), tonumber(y))
+-- [;H            Move cursor to upper left corner
+-- [;f            ^ same
+rules[{"%[", "%d*", ";", "%d*", "[Hf]"}] = function(window, _, y, _, x)
+  set_cursor(window, tonumber(x) or 1, tonumber(y) or 1)
+end
+
+-- [H             move cursor to upper left corner
+-- [f             ^ same
+rules[{"%[[Hf]"}] = function(window)
+  set_cursor(window, 1, 1)
 end
 
 -- [K             clear line from cursor right
@@ -63,14 +71,6 @@ rules[{"%[", "[012]?", "J"}] = function(window, _, n)
   window.gpu.fill(1 + window.dx, y + window.dy, window.width, rep, " ")
 end
 
--- [H             move cursor to upper left corner
--- [;H            ^ same
--- [f             ^ same
--- [;f            ^ same
-rules[{"%[;?", "[Hf]"}] = function(window)
-  set_cursor(window, 1, 1)
-end
-
 -- [6n            get the cursor position [ EscLine;ColumnR 	Response: cursor is at v,h ]
 rules[{"%[", "6", "n"}] = function(window)
   -- this solution puts the response on stdin, but it isn't echo'd
diff --git a/src/main/scala/li/cil/oc/server/PacketSender.scala b/src/main/scala/li/cil/oc/server/PacketSender.scala
index 0b038bc70..7a5218373 100644
--- a/src/main/scala/li/cil/oc/server/PacketSender.scala
+++ b/src/main/scala/li/cil/oc/server/PacketSender.scala
@@ -256,8 +256,10 @@ object PacketSender {
       val x = (xz >> 8).toByte
       val z = xz.toByte
       pb.writeShort(xz)
-      pb.writeInt(t.volume(x + z * t.width))
-      pb.writeInt(t.volume(x + z * t.width + t.width * t.width))
+      val rangeStart: Int = x + z * t.width
+      val rangeFinal: Int = x + z * t.width + t.width * t.width
+      pb.writeInt(t.volume(rangeStart max 0 min t.volume.length - 1))
+      pb.writeInt(t.volume(rangeFinal max 0 min t.volume.length - 1))
     }
 
     pb.sendToPlayersNearTileEntity(t)